1. Technical Field
This invention relates to a water purification system using intense ultraviolet irradiation to break down chemical bonds in toxic compounds and to de-activate pathogens. The method can also be applied to any mass transport, including the purification of air. These systems can be applied to purify fluids containing naturally occurring toxins or those resulting from biological and chemical agents used in warfare.
2. Background Art
The first application of an ultra violet (UV) low-pressure mercury vapor discharge lamp to disinfect water was in Marseilles, France in 1901. However, it was not until 1955 that UV disinfection became widely applied in Europe for potable water. In that year UV disinfection equipment was installed in Switzerland, Austria and Norway. Following the discovery of the formation of halogenated hydrocarbons during chlorination, UV disinfection since became popular in most European countries.
U.S. Pat. No. 1,196,481, issued Aug. 29, 1916 described the use of a mercury vapor lamp to generate sufficient ultraviolet light (mostly 254-nm wavelength) to purify water. This basic approach, built upon the UV efficacy of extended-arc continuous-duty mercury based lamps, has been refined over the years, such as in Ellner U.S. Pat. No. 3,182,193 issued May 4, 1965, Maarschalkerweerd U.S. Pat. No. 4,482,809 issued Nov. 13, 1984, Moyher U.S. Pat. No. 5,069,782 issued Dec. 3, 1991, Tiede U.S. Pat. No. 5,393,419 issued Feb. 28, 1995, and Anderson U.S. Pat. No. 6,099,799 issued Aug. 8, 2000. Much of the latter art improved upon aspects related to commercial viability, such as improving UV dosage uniformity through the use of baffles, UV-transparent coils, and controlled turbulence; increasing UV intensity for higher flow rates by increasing the number of lamps in a given volume; and improving maintenance through the use of Teflon coatings, wiper mechanisms, and adding turbulence.
Prior art UV water disinfecting systems expose the water to UV radiation such that the radiation passes through the water, strikes a reflecting surface and then passes through the water after reflection. The reflecting surfaces absorb a significant amount of radiation. There is a long-felt need to improve the efficiency of such systems.
My invention is an apparatus and method for disinfecting water, or other fluid, that channels water through one end of a tube and couples ultraviolet (UV) energy from a high intensity lamp through the tube from the other end. The water, or other fluid, acts like the core of a liquid light pipe, with an air gap surrounding the tube acting as a low index cladding. The tube itself is constructed of a non-UV-absorbing material, such as UV-grade fused silica glass. Advantageously, the use of light-pipe technology, which is based on total internal reflection (TIR), ensures that all the input UV radiation is dissipated in the water. Preferably, the tube is polygonal in cross-section, which is known in the art to maximize light flux uniformity within a light pipe.
Embodiments of my invention with multiple zones efficiently handle a wide range of water absorption coefficients, all at the highest practical efficiency. In accordance with an aspect of my invention one of three zones is defined by a concentric UV-grade tubing concentrically around only a portion of the tube through which the water flows and others of these zones are defined between these tubes and the enclosing outer tube.